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Thursday, March 19, 2009

Textile consumption

Textile consumption » Changing uses of fabric in apparel

Great changes have occurred in the fabrics used for clothing, with heavy woollen and worsted suitings being replaced by lighter materials, often made from blends of natural and man-made fibres, possibly owing to improved indoor heating. Warp-knitted fabrics made from bulked yarns are replacing woven fabrics, and there is a trend away from formality in both day and evening dress to more casual wear, for which knitted garments are especially appropriate. The use of synthetic fibre fabrics has established the easy-care concept and made formerly fragile light and diaphanous fabrics more durable. The introduction of elastomeric fibres has revolutionized the foundation-garment trade, and the use ofstretch yarns of all types has produced outerwear that is close-fitting but comfortable.

Manufacturers of tailored garments formerly used interlinings made of horsehair, which was later replaced by goat hair and then by resin-treatedviscose rayon. Today fusible interlinings and various washable synthetics are widely used. The performance of a garment is greatly influenced by such factors as the interlining used and the sewing threads employed.

The care required by a textile fabric depends upon both fibre content and the application of various finishing processes. In 1972 the United States Federal Trade Commission passed regulations requiring fabric manufacturers to provide the consumer with care labels to be sewn into homemade garments, and requiring ready-to-wear manufacturers to sew permanent care information labels into clothing (see also clothing and footwear industry).

Dyeing and printing

Textile finishing processes » Dyeing and printing »Dyeing

Most forms of textile materials can be dyed at almost any stage. Quality woollen goods are frequently dyed in the form of loose fibre, but top dyeing or cheese dyeing is favoured in treating worsteds. Manufacturers prefer piece dyeing, which allows stocking of white goods, reducing the risk of being overstocked with cloth dyed in colours that have not been ordered.

The dye used depends on the type of material and the specific requirements to be met. For some purposes, high lightfastness is essential; but for others it may be inconsequential. Factors considered in dye selection include fastness to light, reaction to washing and rubbing (crocking), and the cost of the dyeing process. Effective preparation of the material for dyeing is essential.

Textile finishing processes » Dyeing and printing »Dyeing » Types of dyes

Textile dyes include acid dyes, used mainly for dyeing wool, silk, and nylon; and direct or substantive dyes, which have a strong affinity for cellulose fibres (see Table). Mordant dyes require the addition of chemical substances, such as salts, to give them an affinity for the material being dyed. They are applied to cellulosic fibres, wool, or silk after such materials have been treated with metal salts. Sulfur dyes, used to dye cellulose, are inexpensive, but produce colours lacking brilliance. Azoic dyes are insoluble pigments formed within the fibre by padding, first with a soluble coupling compound and then with a diazotized base. Vat dyes, insoluble in water, are converted into soluble colourless compounds by means of alkaline sodium hydrosulfite. Cellulose absorbs these colourless compounds, which are subsequently oxidized to an insoluble pigment. Such dyes are colourfast. Disperse dyes are suspensions of finely divided insoluble, organic pigments used to dye such hydrophobic fibres as polyesters, nylon, and cellulose acetates.

Fibres and Dyes

fibres                                  application classes    Natural fibres         Animal    Wool                                  acid, basic, mordant, reactive,                                            (solubilized vat)    Wool blends (wool-cotton,             acid, direct, mordant, reactive      wool-viscose, etc.)    Silk                                  acid, basic, direct, mordant, (reactive),                                            (solubilized vat)  Vegetable    Cotton                                azoic, basic, direct, mordant, oxidation,                                            reactive, sulfur, vat    Bast (linen, flax, hemp,              acid, direct, (disperse), reactive, vat,      jute, ramie)                          solubilized vat    Modified cellulose fibres           Viscose                               direct, mordant, pigment, reactive, sulfur,                                            vat, solubilized vat    Secondary acetate                     disperse    Triacetate                            disperse    Synthetic fibres           Polyamide (nylon, Perlon, Rilsan)     acid, disperse, mordant, pigment, reactive    Polyester (Dacron, Terylene)          disperse, pigment    Polyacrylonitrile (Acrilan,           basic, disperse, pigment      Courtelle, Orlon)    Polyvinyl chloride (Envilon,          basic, disperse      Thermovyl)    Polyolefines (Meraklon, Prolene)      disperse    Elastomers (Glospan, Lycra)           acid, disperse, reactive, (wool), vat  

Reactive dyes combine directly with the fibre, resulting in excellent colourfastness. The first ranges of reactive dyes for cellulose fibres were introduced in the mid-1950s. A wide variety is now available.

Textile finishing processes » Dyeing and printing »Dyeing » Application process

The dyeing of a textile fibre is carried out in a solution, generally aqueous, known as the dye liquor or dyebath. For true dyeing (as opposed to mere staining) to have taken place, the coloration must be relatively permanent; that is, not readily removed by rinsing in water or by normal washing procedures. Moreover, the dyeing must not fade rapidly on exposure to light. The process of attachment of the dye molecule to the fibre is one of absorption; that is, the dye molecules concentrate on the fibre surface.

There are four kinds of forces by which dye molecules are bound to fibre: (1) ionic forces, (2) hydrogen bonding, (3) van der Waals’ forces, and (4) covalent chemical linkages. In the dyeing of wool, which is a complex protein containing about 20 different α-amino acids, the sulfuric acidadded to the dyebath forms ionic linkages with the amino groups of the protein. In the process of dyeing, the sulfate anion (negative ion) is replaced by a dye anion. In the dyeing of wool, silk, and synthetic fibres, hydrogen bonds are probably set up between the azo, amino, alkylamino, and other groups, and the amido -CO-NH-, groups. Van der Waals’ forces (the attractive forces between the atoms or molecules of all substances) are thought to act in the dyeing of cotton between the molecular units of the fibre and the linear, extended molecules of direct dyes. Covalent chemical links are brought about in the dyebath by chemical reaction between a fibre-reactive dye molecule, one containing a chemically reactive centre, and a hydroxy group of a cotton fibre, in the presence of alkali.

In any dyeing process, whatever the chemical class of dye being used, heat must be supplied to the dyebath; energy is used in transferring dye molecules from the solution to the fibre as well as in swelling the fibre to render it more receptive. The technical term for the transfer process is exhaustion. Evenness of dyeing, known as levelness, is an important quality in the dyeing of all forms of natural and synthetic fibres; it may be attained by control of dyeing conditions, that is, by agitation to ensure proper contact between dye liquor and substance being dyed, and by use of restraining agents to control rate of dyeing, or strike.

Serious consideration has recently been given to methods of dyeing in which water as the medium is replaced by solvents such as thechlorinated hydrocarbons used in dry cleaning. There are a number of technical advantages in solvent dyeing, apart from the elimination of effluent (pollution) problems associated with conventional methods of dyeing and finishing. Advantages include more rapid wetting of textiles, less swelling, increased speed of dyeing per given amount of material, and savings in energy, because less heat is required to heat or evaporate perchloroethylene, for example, than is needed for water.

For each application the dyer selects the combination of dyes best suited to the particular fibre or blend he plans to dye and best able to withstand the conditions the textile will encounter in further processing and in use in the finished article. In general, the higher the standard of fastness, the more expensive the dye, and the final choice may be a compromise between the desired fastness standards and the cost of the dyes. Fastness tests and standards have been the subject of work by the American Association of Textile Chemists and Colorists (AATCC), Europäisch-Continentale Echtheitsconvention (ECE), and the Society of Dyers and Colourists (SDC), Bradford, West Yorkshire. Efforts have been made to set up a unified system by the International Organization for Standardization (ISO). Lightfastness is assessed on a scale of 8; 1 represents the poorest fastness and 8 the best. Fastness to other agents, among them water, bleach, acid, alkali, detergent solution, and perspiration, is measured on a scale of 5.

Dyes are generally used in combination to achieve a desired hue or fashion shade. If the substance to be dyed consists of only one type of fibre, such as wool, the dye mixture will be made up solely of wool dyes. But if the fabric contains more than one kind of fibre and they differ in dyeing properties, then mixtures of different application classes of dyes are used.

Textile finishing processes » Dyeing and printing »Dyeing » Forms in which textiles are dyed

Loose stock consists of randomly distributed wool or cotton fibres; tow is the corresponding term for synthetic fibres. Sliver is a more orderly arrangement of fibres in a loosely connected, continuous form suitable for spinning. It is wound into either hanks or tops, loose balls about one foot in diameter. After spinning, the yarn is either made up into hanks or into packages weighing about two pounds each, by winding the yarn round perforated metal tubes. The packages are curiously named, some according to their shapes; for example, cones, cheeses, cakes, beams, and rockets. Piece goods, woven cloth or textiles knitted in rope form, and garments, a term that includes stockings, tights, hose, and half hose, are also dyed as such.

Textile finishing processes » Dyeing and printing »Dyeing » Machinery and equipment

Modern dyeing machines are made from stainless steels. Steels containing up to 4 percent molybdenum are favoured to withstand the acid conditions that are common. A dyeing machine consists essentially of a vessel to contain the dye liquor, provided with equipment for heating, cooling, and circulating the liquor into and around the goods to be dyed or moving the goods through the dye liquor. The kind of machine employed depends on the nature of the goods to be dyed. Labour and energy costs are high in relation to total dyeing costs; the dyer’s aim is to shorten dyeing times to save steam and electrical power and to avoid spoilage of goods.

A widely used machine is the conical-pan loose-stock machine; fibres are held in an inner truncated-conical vessel while the hot dye liquor is mechanically pumped through. The fibre mass tends to become compressed in the upper narrow half of the cone, assisting efficient circulation. Levelling problems are less important because uniformity may be achieved by blending the dyed fibres prior to spinning.

The Hussong machine is the traditional apparatus; it has a long, square-ended tank as dyebath into which a framework of poles carrying hanks can be lowered. The dye liquor is circulated by an impeller and moves through a perforated false bottom that also houses the open steam pipe for heating. In modern machines, circulation is improved especially at the point of contact between hank and pole. This leads to better levelling and elimination of irregularities caused by uneven cooling.

In package-dyeing machines dye liquor may be pumped in either of two directions: (1) through the perforated central spindle and outward through the package, or (2) by the reverse path into the outer layers of the package and out of the spindle. In either case levelness is important. In the case of soluble dyes the dye liquor must be free of suspended matter. In the case of disperse dyes, in which particles of dye are dispersed in, rather than dissolved in, the solution, no gross aggregates can be allowed; otherwise the packages would retain undesirable solids on the outer and inner surfaces. Some package-dyeing machines are capable of working under pressure at temperatures up to 130° C.

The winch is the oldest piece-dyeing machine and takes its name from the slatted roller that moves an endless rope of cloth or endless belt of cloth at full width through the dye liquor. Pressurized-winch machines have been developed in the U.S. In an entirely new concept, the Gaston County jet machine circulates fabric in rope form through a pipe by means of a high-pressure jet of dye liquor. The jet machine is increasingly important in high-temperature dyeing of synthetic fibres, especially polyester fabrics.

Another machine, the jig, has a V-shaped trough holding the dye liquor and guide rollers to carry the cloth at full width between two external, powered rollers; the cloth is wound onto each roller alternately, that is, the cloth is first moved forward, then backward through the dye liquor until dyeing is complete. Modern machines, automatically controlled and programmed, can be built to work under pressure.

Solutions or suspensions of colorants or their precursors may be padded onto piece goods by passing the cloth through a trough containing the liquor and then between rollers under pressure. Development and fixation processes such as steaming or dry-heat treatment can be carried out in other apparatus. The method is used in semicontinuous and continuous operations.

Textile finishing processes » Dyeing and printing »Printing

Printing is a process of decorating textile fabrics by application of pigments, dyes, or other related materials in the form of patterns. Although apparently developed from the hand painting of fabrics, such methods are also of great antiquity. There is evidence of printing being carried out in India during the 4th century bc, and a printing block dated at about ad 300 has been unearthed in the burial grounds of Akhmīn inUpper Egypt. Pre-Columbian printed textiles have been found in Peru and Mexico. Textile printing has become highly sophisticated and has involved the skills of many artists and designers.

The four main methods of textile printing are block, roller, screen, and heat transfer printing. In each of these methods, the application of the colour, usually as a thickened paste, is followed by fixation, usually by steaming or heating, and then removal of excess colour by washing. Printing styles are classified as direct, discharge, or resist. In direct printing, coloured pastes are printed directly on the cloth. For discharge printing, the cloth is first dyed with a background colour, which is destroyed by reagents, or reducing agents, carried in a print paste. This action may leave the discharged design white on a coloured background, although print pastes may also contain colouring matters not destroyed by the discharging agent, producing a coloured design. In the resist process, the cloth is first printed with a substance called a resist, protecting these printed areas from accepting colour. When the cloth is dyed or pigment padded only those parts not printed with the resist are dyed. A special application of this technique, imparting plissé effects, is the printing of the fabric with a resist, followed by treatment with caustic soda.

Textile finishing processes » Dyeing and printing »Printing » Block printing

Wooden blocks, carved with a design standing out in relief, are made from solid pieces of wood or by bonding closely grained woods with cheaper ones. When designs include large areas, these are recessed and the space filled with hard wool felt. Fine lines are usually built up with copper strips, and other effects are obtained with copper strips interleaved with felt. To facilitate registration of successive prints, or lays, each block has several pitch pins arranged to coincide with well-defined points in the pattern. Cloth is printed on a table covered with several thicknesses of fabric or blanket, the whole covered with a thick sheet of tightly stretched synthetic rubber. The cloth to be printed is spread on the rubber, either gummed in position or pinned to a backcloth attached to the table. Colour is applied evenly to the block, and the pattern is stamped on the fabric to be printed, using the handle of a small heavy hammer, or maul, to aid penetration of the paste. More colour is then applied to the block and the process is repeated using the pitch pin to obtain true registration. After the fabric has been entirely printed with one colour, other colours are applied in the same way until the design is complete. Although block printing is becoming too laborious and costly for commercial use, some of the most beautiful prints have been made in this way.

Textile finishing processes

Textile finishing processes » Basic methods and processes » Finishes enhancing tactile qualities

Finishes enhancing the feel and drape of fabrics involve the addition of sizing, weighting, fulling, and softening agents, which may be either temporary or permanent.

Textile finishing processes » Basic methods and processes » Finishes enhancing tactile qualities » Sizing

Sizing, or dressing, agents are compounds that form a film around the yarn or individual fibres, increasing weight, crispness, and lustre. Sizing substances, including starches, gelatin, glue, casein, and clay, are frequently applied to cottons and are not permanent.

Textile finishing processes » Basic methods and processes » Finishes enhancing tactile qualities »Weighting

Weighting, in the processing of silk, involves the application of metallic salts to add body and weight. The process is not permanent but can be repeated.

Textile finishing processes » Basic methods and processes » Finishes enhancing tactile qualities »Fulling

Also called felting or milling, fulling is a process that increases the thickness and compactness of wool by subjecting it to moisture, heat, friction, and pressure until shrinkage of 10 to 25 percent is achieved. Shrinkage occurs in both the warp and weft, producing a smooth, tightly finished fabric that may be so compact that it resembles felt.

Textile finishing processes » Basic methods and processes » Finishes enhancing tactile qualities »Softening

Making fabrics softer and sometimes also increasing absorbency involves the addition of such agents as dextrin, glycerin, sulfonated oils, sulfated tallow, and sulfated alcohols.

Textile finishing processes » Basic methods and processes » Finishes improving performance

The performance of fabrics in use has been greatly improved by the development of processes to control shrinkage, new resin finishes, and new heat-sensitive synthetic fibres.

Textile finishing processes » Basic methods and processes » Finishes improving performance »Shrinkage control

Shrinkage control processes are applied by compressive shrinkage, resin treatment, or heat-setting. Compressive, or relaxation, shrinkage is applied to cotton and to certain cotton blends to reduce the stretching they experience during weaving and other processing. The fabric is dampened and dried in a relaxed state, eliminating tensions and distortions. The number of warp and weft yarns per square inch is increased, contributing greater durability, and fabrics treated by this method are usually smooth and have soft lustre. The process involves spraying the fabric with water, then pressing the fabric against a steam-heated cylinder covered with a thick blanket of woollen felt or rubber. The manufacturer is often required to specify the residual shrinkage, or percentage of shrinkage, that may still occur after the preshrinking process.

Rayons and rayon blends may be stabilized by the use of resins, which impregnate the fibre. Such fabrics may also be stabilized by employing acetals to produce cross-linking, a chemical reaction. Such synthetics as polyesters and nylons, which are heat sensitive, are usually permanently stabilized by heat-setting during finishing.

Shrinkage of wools is frequently controlled by treatment with chlorine, partially destroying the scales that occur on wool fibres, thus increasing resistance to the natural tendency of wool to felt. Other methods employ coating with resins that attach to the scales in order to discourage felting shrinkage.

Textile finishing processes » Basic methods and processes » Finishes improving performance » Durable press

Durable press fabrics have such characteristics as shape retention, permanent pleating and creasing, permanently smooth seams, and the ability to shed wrinkles, and thus retain a fresh appearance without ironing. Such fabrics may be safely washed and dried by machine. These useful characteristics are imparted by a curing process. Depending upon composition and desired results, fabrics may be precured, a process in which a chemical resin is added, the fabric is dried and cured (baked), and heat is applied by pressing after garment construction; or fabrics may be postcured, a process in which resin is added, the fabric is dried, made into a garment, pressed, and then cured.

Wash-and-wear was an early durable press process employing chemical treatment and curing of fabrics; at least light ironing was required to restore appearance. Later, however, processes were developed that allowed such fabrics to regain smoothness after home machine washing at moderate temperature, followed by tumble drying.

Textile finishing processes » Basic methods and processes » Finishes improving performance » Crease resistance

Crease, or wrinkle, resistance is frequently achieved by application of asynthetic resin, such as melamine or epoxy.

Textile finishing processes » Basic methods and processes » Finishes improving performance » Soil release

Soil release finishes facilitate removal of waterborne and oil stains from fabrics such as polyester and cotton blends and fabrics treated for durable press, which usually show some resistance to stain removal by normal cleaning processes. Other finishes have been developed that give fabrics resistance to water and oil stains.

Textile finishing processes » Basic methods and processes » Finishes improving performance » Antistatic finishes

The accumulation of static electricity in such synthetic fibres as nylon, polyesters, and acrylics produces clinging, which may be reduced by application of permanent antistatic agents during processing. Consumers can partially reduce static electricity by adding commercial fabric softeners during laundering.

Textile finishing processes » Basic methods and processes » Finishes improving performance »Antibacterial and antifungus finishes

Antibacterial finishes are germicides applied to fabrics to prevent odours produced by bacterial decomposition, such as perspiration odours, and also to reduce the possibility of infection by contact with contaminated textiles. Fabrics may also be treated with germicides to prevent mildew, a parasitic fungus that may grow on fabrics that are not thoroughly dried. Both mildew and rot, another form of decay, may also be controlled by treatment with resins.

Textile finishing processes » Basic methods and processes » Finishes improving performance » Moth-repellent treatments

Wool and silk are subject to attack by moths but may be made moth repellent by the application of appropriate chemicals either added in the dye bath or applied to the finished fabric.

Textile finishing processes » Basic methods and processes » Finishes improving performance »Waterproofing and water repellence

Waterproofing is a process applied to such items as raincoats and umbrellas, closing the pores of the fabric by application of such substances as insoluble metallic compounds, paraffin, bituminous materials, and drying oilsWater-repellent finishes are surface finishes imparting some degree of resistance to water but are more comfortable to wear because the fabric pores remain open. Such finishes include wax and resin mixtures, aluminum salts, silicones, and fluoro-chemicals.

Textile finishing processes » Basic methods and processes » Finishes improving performance »Flameproof, fireproof, and fire-resistant finishes

Flameproof fabrics are able to withstand exposure to flame or high temperature. This is achieved by application of various finishes, depending upon the fabric treated, that cause burning to stop as soon as the source of heat is removed. Fireproofing is achieved by the application of a finish that will cut off the oxygen supply around the flame. Fire-resistant finishes cause fabrics to resist the spread of flame.

Textile finishing processes » Dyeing and printing

Dyeing and printing are processes employed in the conversion of raw textile fibres into finished goods that add much to the appearance of textile fabrics.

Textile finishing processes

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance

Treatments enhancing appearance include such processes as napping and shearing, brushing, singeing, beetling, decating, tentering, calendering or pressing, moiréing, embossing, creping, glazing, polishing, and optical brightening.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance » Napping and shearing

Napping is a process that may be applied to woollens, cottons, spun silks, and spun rayons, including both woven and knitted types, to raise a velvety, soft surface. The process involves passing the fabric over revolving cylinders covered with fine wires that lift the short, loose fibres, usually from the weft yarns, to the surface, forming a nap. The process, which increases warmth, is frequently applied to woollens and worsteds and also to blankets.

Shearing cuts the raised nap to a uniform height and is used for the same purpose on pile fabrics. Shearing machines operate much like rotary lawn mowers, and the amount of shearing depends upon the desired height of the nap or pile, with such fabrics as gabardine receiving very close shearing. Shearing may also be applied to create stripes and other patterns by varying surface height.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance » Brushing

This process, applied to a wide variety of fabrics, is usually accomplished by bristle-covered rollers. The process is used to remove loose threads and short fibre ends from smooth-surfaced fabrics and is also used to raise a nap on knits and woven fabrics. Brushing is frequently applied to fabrics after shearing, removing the cut fibres that have fallen into the nap.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance » Singeing

Also called gassing, singeing is a process applied to both yarns and fabrics to produce an even surface by burning off projecting fibres, yarn ends, and fuzz. This is accomplished by passing the fibre or yarn over a gas flame or heated copper plates at a speed sufficient to burn away the protruding material without scorching or burning the yarn or fabric. Singeing is usually followed by passing the treated material over a wet surface to assure that any smoldering is halted.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance » Beetling

Beetling is a process applied to linen fabrics and to cotton fabrics made to resemble linen to produce a hard, flat surface with high lustre and also to make texture less porous. In this process, the fabric, dampened and wound around an iron cylinder, is passed through a machine in which it is pounded with heavy wooden mallets.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance » Decating

Decating is a process applied to woollens and worsteds, man-made and blended fibre fabrics, and various types of knits. It involves the application of heat and pressure to set or develop lustre and softer hand and to even the set and grain of certain fabrics. When applied to double knits it imparts crisp hand and reduces shrinkage. In wet decating, which gives a subtle lustre, or bloom, fabric under tension is steamed by passing it over perforated cylinders.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance »Tentering, crabbing, and heat-setting

These are final processes applied to set the warp and weft of woven fabrics at right angles to each other, and to stretch and set the fabric to its final dimensions. Tentering stretches width under tension by the use of a tenter frame, consisting of chains fitted with pins or clips to hold the selvages of the fabric, and travelling on tracks. As the fabric passes through the heated chamber, creases and wrinkles are removed, the weave is straightened, and the fabric is dried to its final size. When the process is applied to wet wools it is called crabbing; when applied to synthetic fibres it is sometimes called heat-setting, a term also applied to the permanent setting of pleats, creases, and special surface effects.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance »Calendering

Calendering is a final process in which heat and pressure are applied to a fabric by passing it between heated rollers, imparting a flat, glossy, smooth surface. Lustre increases when the degree of heat and pressure is increased. Calendering is applied to fabrics in which a smooth, flat surface is desirable, such as most cottons, many linens and silks, and various man-made fabrics. In such fabrics as velveteen, a flat surface is not desirable, and the cloth is steamed while in tension, without pressing. When applied to wool, the process is called pressing, and employs heavy, heated metal plates to steam and press the fabric. Calendering is not usually a permanent process.

Moiréing, embossing, glazing and ciréing, and polishing. These are all variations of the calendering process. Moiré is a wavy or “watered” effect imparted by engraved rollers that press the design into the fabric. The process, applied to cotton, acetate, rayon, and some ribbed synthetic fabrics, is only permanent for acetates and resin-treated rayons.Embossing imparts a raised design that stands out from the background and is achieved by passing the fabric through heated rollers engraved with a design. Although embossing was formerly temporary, processes have now been developed to make this effect permanent.

Glazing imparts a smooth, stiff, highly polished surface to such fabrics as chintz. It is achieved by applying such stiffeners as starch, glue, shellac, or resin to the fabric and then passing it through smooth, hot rollers that generate friction. Resins are now widely employed to impart permanent glaze. Ciré (from the French word for waxed) is a similar process applied to rayons and silks by the application of wax followed by hot calendering, producing a high, metallic gloss. Ciré finishes can be achieved without a sizing substance in acetates, which are thermoplastic (e.g., can be softened by heat), by the application of heat.

Polishing, used to impart sheen to cottons without making them as stiff as glazed types, is usually achieved by mercerizing the fabric and then passing it through friction rollers.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance » Creping

crepe effect may be achieved by finishing. In one method, which is not permanent, the cloth is passed, in the presence of steam, between hot rollers filled with indentations producing waved and puckered areas. In the more permanent caustic soda method, a caustic soda paste is rolled onto the fabric in a patterned form; or a resist paste may be applied to areas to remain unpuckered and the entire fabric then immersed in caustic soda. The treated areas shrink, and the untreated areas pucker. If the pattern is applied in the form of stripes, the effect is called plissé; an allover design produces blister crepe.

Textile finishing processes » Basic methods and processes » Finishes enhancing appearance » Optical brightening

Optical brightening, or optical bleaches, are finishes giving the effect of great whiteness and brightness because of the way in which they reflect light. These compounds contain fluorescent colourless dyes, causing more blue light to be reflected. Changes in colour may occur as the fluorescent material loses energy, but new optical whiteners can be applied during the laundering process.